The color an object appears depends on how light energy is absorbed by and reflected from the object. An object's color therefore depends not only on the nature of the object itself, but also on the composition of the light striking it. Different sources of light, such as sunlight, incandescent bulbs, and fluorescent lights, have different spectral power distributions. Therefore, objects can appear differently when viewed under different sources of light. Light sources with different spectral power distributions have different proportions of the various wavelengths of visible light and the reflection and absorption of those different proportions of visible light can result in objects or colors appearing differently when illuminated by different sources of light. Because of this phenomenon, it is common to view a color under more than one light source when performing such color tasks as color selection and color matching. Color stylists want to know what the appearance of an object or color will be under various lighting conditions, such as those present where the color or object will be on display. In addition, when matching one color to another, it is desirable to determine that a match is maintained under various lighting conditions.
Conventional multiple light source devices used for color matching of samples allow only one light source to be selected at a time. These kinds of devices have been used for the critical inspection, evaluation and matching of color with respect to a single light source. These devices are also often used for the aesthetic appraisal of a color under different light sources. Conventional multiple light source devices operate by having one light source on at a time. Each light source illuminates the samples sequentially in order to help a person viewing the samples determine whether two similar colors match. A match of two colors is deemed to be good when those two colors appear identical under all available light sources. However, because of the time lag that occurs when switching from one light source to the next, it is often difficult to judge the closeness of a match or to detect a mismatch due in part to the limited capacity of the user for color memory.
Another type of color evaluation device commonly used is a color rendition demonstrator. Conventional color rendition demonstrators do allow different light sources to be illuminated simultaneously, however, these devices are limited by the fact that they cannot accommodate commonly used light sources (such as long fluorescent light bulbs). Further, conventional color rendition demonstrators do not allow for viewing samples under different light sources simultaneously unless the samples are relatively large or separated by a significant distance, in which case it is more difficult for a user to compare them because the portions of the samples illuminated by different light sources would fall outside of the user's field of view in which subtle differences can be identified.
Therefore, there is a need for a device that can be used to simultaneously illuminate with more than one different light source separate areas of a sample within an appropriately narrow field of view.